Is it possible to rotate hair (object) in timeline?
I'm not sure how well this technique can be adapted to your situation--it looks like your bugs are largish objects, and I think getting the rotation correct (so the bugs are correctly oriented to the surface) might be hard with any particle system solution.

But if it's useful to you, I can explain how to get an effect like this one:



The bugs are small symmetrical objects (icospheres) that move using brownian motion and are confined to essentially the surface of the sphere by invisible collision objects (also spheres) just below and above the desired "shell" of motion.